Department of Biology, College of Science, University of Bahrain, Sakhir Campus P. O. Box 32038, Sakhir, Bahrain. Gastroenterology and Digestive Endoscopy Unit, Centro Diagnostico Italiano, 20147 Milan, Italy. Endocrinology and Nutrition Unit, Azienda di Servizi alla Persona ''Istituto Santa Margherita'', University of Pavia, 27100 Pavia, Italy. Research and Development Unit, Indena SpA, 20139 Milan, Italy. Department of Chemistry, College of Science, University of Bahrain, Sakhir Campus P. O. Box 32038, Sakhir, Bahrain. Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy. Istituto di Ricovero e Cura a Carattere Scientifico, Mondino Foundation, 27100 Pavia, Italy.